Method of prevention of corrosion in wells



Patented Got. 21, M52

METHOD OF PREVENTION OF GURROSION IN WELLS .ioseph A. @aldwell and Melba. L. Lytle, Houston,

Tex.,

assignors, by mesne assignments, to

Standard Oil Development Company, Elizabeth, I a Y N. 3., a corporation of Delaware No Drawing.

Application April 3, 1950,

Serial No. 153,769

8 Claims.

This invention relates to a method of inhibiting the corrosiveness to corrodible ferrous metal surfaces ofcorrosive fluids containing hydrogen sulfide. More particularly, the invention relatesto means for inhibiting the corrosivity of sulfide-containing, subsurface formation fluids to the corrodible conduits and attendant equipment through which the fluids are flowed and processed.

Crude oil containing soluble sulfides is often produced from subsurface formations and corrosion of conduits and attendant equipment is especially severe in those instances in which brine is produced along with the sour crude. Corrosive sulfide brines may include alkali metal sulfides, alkaline earth metal sulfides, acid sulfides such as hydrogen sulfide, and/or organic sulfides. Those brines containing hydrogen sulfide are especially corrosive to iron and steel equipment, the sulfides attacking the metal to form iron sulfide. Since these corrosive substances occur in or are introduced into the fluids originating in the subsurface formations, corrosion may occur throughout the conduits and attendant equipment through which the fluids from the subsurface formations are flowed and produced. In other cases the corrosion may be more or less localized to a limited portion of the conduits through which the fluids from the subsurface formations are produced. In any case, corrosion of the conduits and/or attendant equipment may be so severe as to require replacement of either or of both. Such replacements can be, and often are, extremely expensive. The expense involved is not limited merely to the cost of replacing the corroded equipment but may also involve killing the well in order to make repairs and to replace the corroded equipment. Not only is the cost of killing the well high but there is a marked loss in revenues due to having a well off production and to the necessity of having to maintain additional wells and sources of supply to meet production requirements during the period when the well is off production for repairs as a result of the corrosion. Corrosion may, on occasion, be so severe as to result in failure of the equipment in which event the well may flow wild. Enormous losses are incurred in such an eventuality.

The main object of the present invention is to provide a method of substantially eliminating or inhibiting the corrosive action of subsurface fluids containing sulfides to conduits and attendant equipment through which the fluids. are produced from the subsurface formations in which they originate.

In accordance with the present invention, corrosion of ferrous metal surfaces is inhibited or substantially eliminated by adding to fluid mixtures produced from subsurface formations and containing sulfides a small amount of fatty derivatives of polyethylene glycols. The lower molecular weight polyethylene glycols do not yield fatty derivatives which have practical effectiveness in inhibiting corrosion of ferrous metal surfaces by well fluids containing sulfides. For example, the fatty derivatives .of mono-, di-, tri-ethylene glycols are either completely ineffective or must be used in prohibitive quantities to effect substantial inhibition. The most generally suitable and powerful fatty derivatives of polyethylene glycols are derived from polyethylene glycols of the type formula in which C designates carbon, H designates hydrogen, O designates oxygen, and X has a value of from 3 to 30. It is preferred to employ a polyethylene glycol in which the value of X in the foregoing formula is in the range of'6 to 15. The (OC2H4) group in the foregoing formula will hereinafter be designated, for the sake of simplicity, as an ethanoxy group. Fatty derivatives prepared from nonaethylene'glycol; for example, are particularly effective. Other poly ethylene glycols which may be mentioned by Way of example include: tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, heptaethylene glycol, octaethylene glycol, decaethylene glycol, dodecaethylene glycol, tridecaethylene gly-; col, pentadecaethylene glycol, etc. t

The fatty material employed to produce the fatty derivatives of polyethylene glycol may be selected from the class of fatty acids and fatty oils.

donic, lauric, myristic, arachidic, stearic, palmi-tic, etc. and fatty oils from which such acids can be derived may be reacted with the polyethylene Acids having from 12 to 26 carbon atoms per molecule such as palmitoleic, oleic, ricinoleic, linoleic, linolenic, licanic, arachidonic, clupano-- glycols to produce the desired corrosion inhibiting agents. Especially effective agents are obtained by reacting the polyethylene glycols with such fatty oils as linseed oil, cottonseed oil, tung oil, oiticica, oil, China-wood oil, menhaden oil, and the like, or mixtures thereof. Likewise, mixtures of polyethylene glycols may be employed. In any event, the fatty material selected is reacted with the polyethylene glycol selected at a temperature in the range. of from 300 to550 F fora time in the range-offrom 1 to 5 hours in-the presence of a small amount of an alkaline reacting catalyst such as an alkali hydroxide or carbonate or mix-.- tures thereof. The fatty derivatives of polyethyene glycols prepared in the foregoing manner are soluble in many aromatic solvents and, to a more limited extent, in petroleum. solvents such as heavy naphtha or kerosene.

The polyethylene glycols which are-employed in the preparation of the fatty derivatives of the present invention are readily available. They 1 may be made, for example, by reacting ethylene oxide with water, the formation of polyethylene glycols being favored by maintaining the' molal ratio of ethylene oxide to water in excess of 1. Thedegree of polymerization is determinedlby theireaction conditions maintained. Polyethyl ene glycolshaving molecular weights-in excess of 1500' are commercially available as well as polyethylene glycols having lower:- molecular weights. For use in the preparation of the fatty derivatives employed in accordance with the prescut-invention, it is'not necessary that the polyethylene glycols :be separated-into close fractions of narrowrmolecular weightlimits; on'the contrary, fractions including-a large numberof pol'y mers' of; different molecular. weights may beemployed.

When fatty derivatives of the presentinventionz are. preparedfromafatty oil and, polyethylene glycol, itis preferable that the fatty oil be present in-the vinitial reactionmixture in a weight ratiooffrom about 1:1 to about 3il as compared tofithe polyethylene glycol. derivative is prepared from a-fattyacid', thefatty a'cidiishould be present in the initial reaction mixture in a Weight ratio'of-from about 0.'5':l toabout 2:1 as compared to the polyethylene glycol. Only a small amount .of the alkaline. reacting catalyst need be present, and ordinarily no more than 3 weightv per' cent of the. catalystbased on: the' weight-of the reaction mixture is employed. For example, aconcentration of 1 weight percent of sodium-hydroxide based on the Weight of the re-' actantshas-been found sufficientto promote the reaction, On the other hand, aslittle as 0.5 weight per cent of sodium hydroxide based'upon the. weight of the reactants has been found sufiicient when from about 0.5 weight per cent to about 2.0'weight percentof. sodium carbonate is :utilized as a co-catalyst. 0.05'Weight per cent-of sodiumhydroxide: gave goodzresults. 1

Thez'amount ofrfattyiderivative of the present invention employed to inhibit- -the corrosion of ferrous metal surfaces. by well fluid mixtures, containing hydrogen sulfide may be varied over a relatively wide range although it has been found that amounts within the range of 0.005 per cent to 0.-1,-.per cent by volume of the fiuid mixture give satisfactory results. Ordinarily, however, an amount within the range of 0.005 per cent to 0.01 per centwill give'satisfactory inhibition.

Inasmuch as the fatty-derivative of the present invention is soluble in' certain solvents heretofore When the fatty In another instance.

, F. for a'period of 2 hours.

mentioned, it may be found convenient to dissolve the fatty derivative in a, suitable solvent before introducing it into the corrosive fluid mixture. When it is desired to protect from corrosion the conduit in the borehole, the fatty derivative or a solution thereof may be injected into the borehole adjacent the subsurface formation from which the corrosive fluid, including hydrogen sulfide, is produced or it may be introduced-directl'y into the conduit through which the corrosive fluid flows from the subsurface formation to the surface of the earth. A still further method of introducing the fatty derivative into the fluids produced from the subsurface formation involves introducing the fatty derivative or a solution thereof into the annular space between. thecasing and the tubing. Another method: of introducing the fatty derivative into the subsurface fluid consists of injecting the fatty material or-a solution thereof into the subsurface reservoir through "an adjacent well. Irrespective of theLp-articular procedure employed in introducing .the fatty derivative into the fluids in the well, the fatty derivative suppresses the corrosivity of the fluid, thereby eliminating or reducing damage to the conduitthroug-h which the Example I.

Mild carbon steel coupons were immersed 312 times perrminute $01214: days; inza. mixturescontaining,,50 :cc; of West .Texa'stbrineiand :cc.' off West .Texas' crude, .thermixturetbeing saturated with hydrogen sulfide. Air. was: excluded: from" the mixture. No inhibitor wast-added tOTthiSSfiISt mixture and it was employed asxa: control; An other mild carbon steel couponrwasimmersedfil;

times per minute for 14' days in a mixture identical with the first mixture-exceptithati .01.:per3

centby-volume of the' reaction' product" of ftung oil and nonaethylene glycol wasadded; A' third:

carbonsteel coupon wasimmersed 31 times .per

minute for 14 days in a; mixture identicalwith' the first mixture except that 0.005 per: cent -.by volume of the reaction product of tunggoil and: nonaethylene-glycol.was added; This reaction productwas prepared as follows: 60;gram'svof: Chinese tungoil, 410 gramsiof nonaethylene glycol, and'0.5 gram of sodium'hydroxide were heated: together'at a temperature of from-500 F. to 550 on completion of:.thereaction period, the reactionmixture was coole'd to roomitemperature; The results obtained'in the aforementioned tests are shown in Table I:"

TABLE I Concentration of Inhibitor in Corrosive Fluid, Percent Percent Reduction inOorrosion Over Blank Because the aforementioned laboratory: tests? indicated :the marked effectiveness voft'fatty dot-- rivativesiof polyethylene glycol as an inhibitoriof the'corrosivity of well fluids containing hydrogen sulfide, the reaction product of Chineseitung oil and nonaethylene glycol prepared in theimanrrerr hereinbefore indicated was: field tested; This s field test was-=carried=out by suspending mild steel coupons in the flowlines of two different .wells', ,eachyof which was locatedin a different field; eachwell producing fluids-containingyhydrogen'sulfide. Each coupon was retained'in-the flow line prior to inspection for a period of at least one week,.andi.one coupon was allowed to remaininthe flowline for aperiodof approximately 26 weeks. During certain portions of [the test period the reaction product of Chinese tung oil and nonaethylene glycol was injected into the well fluids through the annulus between the casing and the tubing. The results obtained are tabulated below in Table II:

TABLE II Water Rate of Rate of Produc- 01-1 Inhibitor Time of Metal Well tion, duction Injection, Exposure, LOSS Percent Bus/Day Qts./Day Days In./Yr

s5 5 2s 0. 0018 #1 s 5 0 30 0.0021 85 5 n 1% 11 0. 0000 85 5 1 35 0. 0003 50 25 0 31 0.031 50 25 o 29 0.005 50 25 0 7 0.022 #2 50 25 0 25 0. 032 50 25 0 184 0.012 50 25 1 20 0.028 50 25 1 29 0. 0009 50 25 1 03 0.0035

Inhibitor consisted of 88% reaction product of nonaethylene glycol and Chinese tung oil and 12% xylene by weight.

b Injection started 15 days prior to installation of coupon.

Injection started 8 days prior to installation of coupon.

As indicated by the data in Table II, the reaction product of Chinese tung oil and nonaethylene glycol, in every case in which it was used, effected a marked reduction in the corrosion of the mild steel coupons.

Data on the material failures in well #2 support the evidence of the effectiveness of inhibition. Prior to the time that any inhibitor was injected into this well, a string of new tubing coated inside and out with a baked-on plastic was installed in the well. It was necessary to pull this tubing four times within the next 66 days following its installation because of failure of one or more joints, either by complete penetration of the pipe or by failure in the threads.

When it became necessary to pull the aforementioned tubing for the fourth time, it was replaced by a string of new, uncoated pipe. This newly installed string of pipe had to be removed and partly replaced in less than 3 months because one joint had corroded through. This same well, prior to the use of an inhibitor therein, had a further history of failures due to corrosion. For example, uncoated tubing has at times failed in 4 weeks and pump working barrels have failed in 30 days. In contrast to this history of repeated failures of the tubing in the well due to corrosion, no tubing failures occurred over a period of approximately 5 months from the time the inhibitor made from Chinese tung oil and nonaethylene glycol was first injected. Thus by injection of the aforementioned inhibitor into well fluids from this well, a marked reduction in corrosion of ferrous metal surfaces was obtained.

It will be observed from the data presented above that the addition of a small amount of a fatty derivative of polyethylene glycol effects a marked reduction in the tendency of a corrosive fluid) solution containing hydrogen sulfide to corrode ferrous metal.

The nature and objects of the present invention having been fully described and illustrated,

what we wish to claim as new and useful and. to I secure by Letters Patent is: I

1. A-methodfor reducing the corrosiveness to sulflde which comprisesintroducing into said fluid a corrosion inhibiting amount of a reaction product obtained by reacting a fatty material selected from the group consisting of fatty acids having at least 12"and no more'than 26 carbon atoms per molecule. and fatty. oils. containing fatty acid radicals having nolless than 12 and no more than 26 carbon atoms in the radical witha polyethylene glycol containing at least 3 and no more than 30 ethanoxy groups at a temperature in the range of 300 to 550 F. for a period of from 1 to 5 hours in the presence of an alkaline reacting catalyst selected from the group consisting of alkali metal hydroxide and alkali metal carbonate, the weight ratio of fatty material to polyethylene glycol being in the range of 1:1 to about 3:1.

2. A method in accordance with claim 1 in which the reaction product is added to the corrosive fluid in an amount within the range of 0.005% to 0.1% by volume of the fluid.

3. A method for reducing the corrosiveness to corrodible ferrous metal of a corrosive petroliferous well fluid including moisture and hydrogen sulfide which comprises introducing into said fluid a corrosion inhibiting amount of a reaction product formed by heating tung oil and nonaethylene glycol together for a period of from 1 to 5 hours at a temperature in the range of 300 to 550 F. in the presence of an alkaline reacting catalyst selected from the group consisting of alkali metal hydroxide and alkali metal carbonate, the weight ratio of tung oil to nonaethylene glycol being in the range of 1:1 to about 3:1.

4. A method in accordance with claim 3 in which the reaction product is added to the corrosive fluid in an amount within the range of 0.005% to 0.1% by volume of the fluid.

5. A method for reducing the corrosiveness to corrodible ferrous metal of a corrosive petroliferous well fluid including moisture and hydrogen sulfide which comprises introducing into said fluid a corrosion inhibiting amount of a reaction product formed by heating cottonseed oil and nonaethylene glycol together for a period of from 1 to 5 hours at a temperature in the range of 300 to 550 F. in the presence of an alkaline reaction catalyst selected from the group consisting of alkali metal hydroxide and alkali metal carbonate, the weight ratio of cottonseed oil to nonaethylene glycol being in the range of 1:1 to about 3:1.

6. A method in accordance with claim 5 in which the reaction product is added to the corrosive fluid in an amount within the range of 0.005% to 0.1% by volume of the fluid.

7. A method for reducing the corrosiveness to corrodible ferrous metal of a corrosive petroliferous well fluid including moisture and hydrogen sulfide which comprises introducing into said fluid a corrosion inhibiting amount of a reaction product formed by heating oiticica oil and nonaethylene glycol together for a period of from 1 to 5 hours at a temperature in the range of 300 to 550 F. in the presence of an akaline reaction catalyst selected from the group consisting of alkali metal hydroxide and alkali metal carbonate, the weight ratio of oiticica oil and nona- 7 8 ethylene glycol being in the range of 1:1 to UNITED STATES PATENTS about Number I Name D 8. A method in accordance with claim '7 in 2249 800 Weber Julygaztelgzu which the reaction product is added to the cor- 2460259 f' Jan 1949 rosive fluid in an amount within the range of 5 Moore :1 1950 0.005% to 0.1% by volume of the fluid. u

g a f g fi OTHER REFERENCES Ind. 8z Eng. Chem., V01. 40, No. 12, page 2344. REFERENCES CITED 10 Article by Baker et a1.

The following references are of record in the file of this patent: 

1. A METHOD FOR REDUCING THE CORROSIVENESS TO CORRODIBLE FERROUS METAL OF A CORROSIVE PETROLIFEROUS WELL FLUID INCLUDING MOISTURE AND HYDROGEN SULFIDE WHICH COMPRISES INTRODUCING INTO SAID FLUID A CORROSION INHIBITING AMOUNT OF A REACTION PRODUCT OBTAINED BY REACTING A FATTY MATERIAL SELECTED FROM THE GROUP CONSISTING OF FATTY ACIDS HAVING AT LEAST 12 AND NO MORE THAN 26 CARBON ATOMS PER MOLECULE AND FATTY OILS CONTAINING FATTY ACID RADICALS HAVING NO LESS THAT 12 AND NO MORE THAN 26 CARBON ATOMS IN THE RADICAL WITH A POLYETHYLENE GLYCOL CONTAINING AT LEAST 3 AND NO MORE THAN 30 ETHANOXY GROUPS AT A TEMPERATURE IN THE RANGE OF 300* TO 550* F. FOR A PERIOD OF FROM 1 TO 5 HOURS IN THE PRESENCE OF AN ALKALINE REACTING CATALYST SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL HYDROXIDE AND ALKALI METAL CARBONATE, THE WEIGHT RATIO OF FATTY MATERIAL TO POLYETHYLENE GLYCOL BEING IN THE RANGE OF 1:1 TO ABOUT 3:1. 